Answer:
1. they should not trust them.
2. its an example of pseudoscience.
Reasons:
Reason 1: They paid the scientists, so they are biased.
Reason 2: the 50 people claimed to have a headache, it wasn’t proven that they did.
Reason 3: They didn’t have another group of people drinking regular water, so you don’t know if just drinking water cures it, not their special water.
hope this helps! :)